Continuously variable transmission and transmission system

Abstract

The invention relates to a continuously variable transmission and a transmission system comprising said continuously variable transmission, wherein the continuously variable transmission comprises a first gear pump and a second gear pump, wherein each gear pump comprises a first gear and a second gear meshing with the first gear over an overlap distance in an overlap direction parallel to the first gear axis, wherein each gear pump further comprises an adjustment member for adjusting the pump volume, wherein the adjustment member of the first gear pump and the adjustment member of the second gear pump are interconnected by a connecting member for adjusting the pump volume of the first gear pump and the pump volume of the second gear pump in an inverse correlation to each other.

The invention claimed is: 
     
       1. A continuously variable transmission comprising:
 a first gear pump, and a second gear pump, 
 wherein each gear pump comprises a fluid inlet, a fluid outlet and a pump volume between the fluid inlet and the fluid outlet, 
 wherein each gear pump further comprises a first gear rotatable within the respective pump volume about a first gear axis and a second gear rotatable within the respective pump volume about a second gear axis and meshing with the first gear over an overlap distance in an overlap direction parallel to the first gear axis for displacing fluid through the respective pump volume from the respective fluid inlet to the respective fluid outlet, 
 wherein the fluid outlet of the first gear pump is arranged in fluid communication with the fluid inlet of the second gear pump and the fluid outlet of the second gear pump is arranged in fluid communication with the fluid inlet of the first gear pump, 
 wherein each gear pump further comprises an adjustment member for adjusting the pump volume of the respective gear pump, 
 wherein the adjustment member of the first gear pump and the adjustment member of the second gear pump are interconnected by a connecting member that is arranged for adjusting the pump volume of the first gear pump and the pump volume of the second gear pump in an inverse correlation to each other. 
 
     
     
       2. The continuously variable transmission according to  claim 1 , wherein the inverse correlation is an inverse proportionality. 
     
     
       3. The continuously variable transmission according to  claim 2 , wherein the inverse proportionality is such that the ratio between an increase of one of the first pump volume and the second pump volume and a decrease of the other of the first pump volume and the second pump volume is 1:1. 
     
     
       4. The continuously variable transmission according to  claim 1 , wherein the connecting member mechanically interconnects the adjustment member of the first gear pump and the adjustment member of the second gear pump. 
     
     
       5. The continuously variable transmission according to  claim 1 , wherein the connecting member is arranged for hydraulically interconnecting the adjustment member of the first gear pump and the adjustment member of the second gear pump with the use of a hydraulic circuit separate from the pump volume of the first gear pump and the pump volume of the second gear pump. 
     
     
       6. The continuously variable transmission according to  claim 1 , wherein each adjustment member is arranged for providing a relative movement between the first gear and the second gear of the respective gear pump in the respective overlap direction. 
     
     
       7. The continuously variable transmission according to  claim 1 , wherein each adjustment member is arranged for holding one of the first gear and the second gear of the respective gear pump and is movable in the respective overlap direction in unison with said one of the first gear and the second gear. 
     
     
       8. The continuously variable transmission according to  claim 1 , wherein each gear pump further comprises a holding member opposite to the adjustment member of the respective gear pump in the respective overlap direction for holding one of the first gear and the second gear of the respective gear pump,
 wherein the holding member and the adjustment member comprise a first sealing surface and a second sealing surface, respectively, for sealing the pump volume of the respective gear pump in the respective overlap direction between the holding member and the adjustment member of the respective gear pump, 
 wherein the second sealing surface is movable in the respective overlap direction towards and away from the first sealing surface. 
 
     
     
       9. The continuously variable transmission according to  claim 1 , wherein each gear comprises a first gear part with a plurality of first gear teeth distributed circumferentially about the respective gear axis and a second gear part with a plurality of second gear teeth distributed circumferentially about the same gear axis,
 wherein the first gear teeth and the second gear teeth are slidable along each other in the respective overlap direction for telescopically extending or contracting the respective gear in the respective overlap direction. 
 
     
     
       10. The continuously variable transmission according to  claim 1 , wherein the first gear pump and the second gear pump are external gear pumps. 
     
     
       11. The continuously variable transmission according to  claim 1 , wherein one of the first gear and the second gear is an internal gear and the other of the first gear and the second gear is an external gear with less teeth than and meshing with the internal gear,
 wherein the first gear pump and the second gear pump are internal gear pumps. 
 
     
     
       12. The continuously variable transmission according to  claim 1 , wherein one of the first gear and the second gear is an internal gear and the other of the first gear and the second gear is an external gear with less teeth than and meshing with the internal gear,
 wherein the first gear pump and the second gear pump are gerotor gear pumps. 
 
     
     
       13. The continuously variable transmission according to  claim 1 , wherein the continuously variable transmission further comprises a control member for controlling the adjustment members of the respective gear pumps. 
     
     
       14. The continuously variable transmission according to  claim 13 , wherein the control member is a lever that is operationally coupled to the adjustment member of the first gear pump, the adjustment member of the second gear pump or the connecting member. 
     
     
       15. The continuously variable transmission according to  claim 13 , wherein each gear pump comprises one or more chambers separated from the pump volume of the respective gear pump,
 wherein each chamber has a chamber volume that is arranged to absorb the expansion of the pump volume of the respective gear pump, 
 wherein the control member comprises an hydraulic circuit interconnecting at least two of the chambers and a drive pump for pumping hydraulic fluid from one of said two chambers to the other of said two chambers. 
 
     
     
       16. The continuously variable transmission according to  claim 1 , wherein one of the first gear axis and the second gear axis of the first gear pump is coaxial with one of the first gear axis and the second gear axis of the second gear pump. 
     
     
       17. The continuously variable transmission according to  claim 1 , wherein the first gear axis of the first gear pump is out of line with the first gear axis of the second gear pump or wherein the second gear axis of the first gear pump is out of line with the second gear axis of the second gear pump. 
     
     
       18. A transmission system comprising the continuously variable transmission according to  claim 1 , wherein the transmission system comprises a source of energy and one or more parts to be driven by said source of energy,
 wherein the continuously variable transmission is arranged between the source of energy and the one or more parts to be driven. 
 
     
     
       19. The transmission system according to  claim 18 , wherein the continuously variable transmission is arranged in-line or in series with the source of energy and the one or more parts to be driven. 
     
     
       20. A continuously variable transmission comprising:
 a first gear pump, and a second gear pump, 
 wherein each gear pump comprises a fluid inlet, a fluid outlet and a pump volume between the fluid inlet and the fluid outlet, 
 wherein each gear pump further comprises a first gear rotatable within the respective pump volume about a first gear axis and a second gear rotatable within the respective pump volume about a second gear axis and meshing with the first gear over an overlap distance in an overlap direction parallel to the first gear axis for displacing fluid through the respective pump volume from the respective fluid inlet to the respective fluid outlet, 
 wherein each gear pump further comprises an adjustment member for adjusting the pump volume of the respective gear pump, 
 wherein the adjustment member of the first gear pump and the adjustment member of the second gear pump are interconnected by a connecting member that is arranged for adjusting the pump volume of the first gear pump and the pump volume of the second gear pump in an inverse correlation to each other, wherein the continuously variable transmission further comprises a control member for controlling the adjustment members of the respective gear pumps, and 
 wherein the control member comprises a switch element for switching between a first state in which the fluid outlet of the first gear pump is arranged in fluid communication with the fluid inlet of the second gear pump and the fluid outlet of the second gear pump is arranged in fluid communication with the fluid inlet of the first gear pump and a second state in which the fluid outlet of the first gear pump is arranged in fluid communication with the fluid outlet of the second gear pump and the fluid inlet of the second gear pump is arranged in fluid communication with the fluid inlet of the first gear pump.